On Tue, May 13, 2014 at 12:58:23PM -0700, Todd E Brandt wrote: > This patch creates a separate instance of the usb_address0 mutex for each host > controller, and attaches it to the host controller device struct. This allows > devices on separate hosts to be enumerated in parallel; saving time. > > In the current code, there is a single, global instance of the usb_address0 > mutex which is used for all devices on any host. This isn't completely > necessary, as this mutex is only needed to prevent address0 collisions for > devices on the *same* host (usb 2.0 spec, sec 4.6.1). This superfluous > coverage > can cause additional delay in system resume on systems with multiple hosts > (up to several seconds depending on what devices are attached). > > For instance, if I have a USB WLAN and a KVM switch attached to two ports, > there's a chance that they could be initialized at the same time (e.g. on > system resume). They would both be in the Default state and would be > responding to requests from the default address (address 00H). If they were > on the same host, there'd be no way of differentiating the two devices and > thus > the mutex is needed. But on separate hosts there's no chance of collision. > > Signed-off-by: Todd Brandt <[email protected]> > --- > drivers/usb/core/hcd.c | 15 +++++++++++++-- > drivers/usb/core/hub.c | 6 ++---- > include/linux/usb/hcd.h | 1 + > 3 files changed, 16 insertions(+), 6 deletions(-) > > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c > index 9c4e292..b5d89eb 100644 > --- a/drivers/usb/core/hcd.c > +++ b/drivers/usb/core/hcd.c > @@ -2452,9 +2452,18 @@ struct usb_hcd *usb_create_shared_hcd(const struct > hc_driver *driver, > return NULL; > } > mutex_init(hcd->bandwidth_mutex); > + hcd->usb_address0_mutex = > + kmalloc(sizeof(*hcd->usb_address0_mutex), GFP_KERNEL); > + if (!hcd->usb_address0_mutex) { > + kfree(hcd); > + dev_dbg(dev, "hcd usb_address0 mutex alloc failed\n");
No need to ever do a "allocation failed" message, as kmalloc would have just done that if it did fail. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
